Can we update contact without having Infusion ContactID

Can we update contact without having Infusion ContactID? Means by using other thing like emal id or anything.
Actually I need to update contact, but dont want to keep infusion contactId into my database, is there any way.

To actually preform an update, you will need the id. That is the only truly unique identifier for contacts as it is possible to have multiple contacts with the same email address. You can, however, use the findByEmail method to get the id of a contact but that method returns an array (which could have more than one contact). So if you ensure that your contacts are only using unique emails addresses, then you can use the findByEmail method that would then return an array of one contact. Request the id as part of the return fields so that you will then be able to submit the update to that contact.